1. Field of the Invention
This invention relates to an improved ebullated bed process. In the improved process a hydrogen-containing gas comprising elevated amounts of hydrogen sulfide is introduced into the reactor and as a result sediment formation is surpressed.
2. Description of Other Relevant Methods in the Field
The ebullated bed process comprises the passing of concurrently flowing streams of liquids or slurries of liquids and solids and gas through a vertically cylindrical vessel containing catalyst. The catalyst is placed in random motion in the liquid and has a gross volume dispersed through the liquid medium greater than the volume of the catalyst when stationary. The ebullated bed process has found commercial application in the upgrading of heavy liquid hydrocarbons such as vacuum residuum or atmospheric residuum or converting coal to synthetic oils. The ebullated bed process is generally described in U. S. Pat. No. Re. 25,770 issued Apr. 27, 1965 to E. S. Johanson.
U. S. Pat. No. 4,465,584 to E. Effron et al teaches the use of hydrogen sulfide to reduce the viscosity of a bottoms stream produced in a hydroconversion process. Coal, petroleum residuum and similar carbonaceous feed materials are subjected to hydroconversion in the presence of a hydrogen-containing gas to produce a hydroconversion effluent which is subjected to separation to yield a heavy bottoms stream containing high molecular weight liquids and unconverted carbonaceous material. The viscosity of the bottoms stream produced in the separation stage is prevented from increasing by treating the feed to the separation stage with hydrogen sulfide gas prior to or during separation. The heavy bottoms may be stored in an atmosphere of gaseous hydrogen sulfide in order to prevent polymerization and degradation prior to further processing.
U. S. Pat. No. 4,457,834 to J. Caspers et al teaches an ebullated bed process in which gaseous products are recovered from a catalytic hydrogenation zone. Contaminants such as hydrogen sulfide are removed from the gaseous products to yield a hydrogen gas containing at least 70 vol % hydrogen.
U. S. Pat. No. 3,681,231 to S. B. Alpert et al discloses an ebullated bed process for the production of fuels such as diesel oil. A crude feedstock and an aromatic diluent is passed to an ebullated bed at a temperature of 600.degree. F. to 900.degree. F., pressure of 500 to 5000 psig and a hydrogen partial pressure in the range of 65% to 95% of total pressure. It was found that 20 to 70 vol % of an aromatic diluent having a boiling point in the range of 700.degree. F. t o 1000.degree. F. (heavy gas oil) injected in the feed reduced the amount of insoluble material in the product.
U. S. Pat. No. 4,446,002 to C. W. Siegmund teaches a process for suppressing the precipitation of sediment in unconverted residuum obtained from a virgin residuum conversion process. The process comprises blending the unconverted residuum with an effective amount of a virgin residuum.